Metabolic factor

Metabolic factors. Hypercalciurea or cystinurea, for example, facilitate the formation of calculi. 

The brain has an absolute dependence on the blood for its immediate supply of oxygen and energy substrates. Interruption of oxygen or substrate supply by compromise of pulmonary or cardiovascular function or metabolic factors results in encephalopathy and, if prolonged, neuronal cell death. The brain uses approximately 20% of the total oxygen supply of the body. While glucose remains the primary energy substrate for the brain, alternative substrates maybe used under certain circumstances (see Ch. 31). 

Therefore the catalytic activity of these enzymes varies enormously and it is in theory possible that at least in some cases the quantity or activity of the hydrogen evolving enzyme could limit the overall process. However, there is little evidence for this being the limiting factor in any system. Indeed, in many microbial systems, potential catalytic activity far surpasses the amount of hydrogen produced, suggesting that other metabolic factors are limiting. 

E. Tornberg, A. Andersson, A. Goransson and G. von Seth, Pork Quality Genetic and Metabolic Factors, CAB International, UK, 239. 

Use of in vivo Tests. In vivo tests are more relevant indicators than are in vitro tests of immunotoxicity since the dynamic interactions between the various immuno-components, as well as the pertinent pharmacokinetic (absorption, distribution, plasma concentrations) and metabolic factors, are taken into consideration. However, it is important to select the appropriate animal model and to design the protocol such that it will accurately reflect drug (or relevant metabolite) exposure to humans. For example, one should consider species variability when selecting the animal model, since biological diversity may further obscure the ability to accurately predict human toxicity. 

Guzelian, PS. and Bissell, D.M. (1974). Metabolic factors in the regulation for cytochrome P-450. Studies in rat hepatocyte monolayer culture. FedProc. 33 1246. 

Masubuchi, Y. (2006) Metabolic and non-metabolic factors determining troglitazone hepatotoxicity a review. Drug Metabolism and Pharmacokinetics, 21 (5), 347-356. 

Ostrovsky YuM, Sadovnik MN, Satanovskaya VI, et al. Metabolic factors and preference for ethanol. Pharmacology, Biochemistry Behavior 1983 18 Suppl. 1 5315. 

Both physiological and metabolic factors play a role in regulation of blood pressure. The former involves the vasomotor centre at the base of the brain and the basoreceptor located in the carotid sinus and the aortic arch. These mechanisms provide short-term regulation of the blood pressure, which is not discussed in this book. 

Some people are rapid metabolizers of drugs and some are slow metabolizers. Factors that can affect the response to drugs... 

Remmer H. In Brodie BB, Erdos EG, eds. Metabolic Factors Controlling Duration of Drug Action, Proceedings of First International Pharmacological Meeting, Vol. 6. New York Macmillan, 1962. 

A 60-year-old woman with normal liver function tests developed acute hepatitis 6 weeks after starting to take gliclazide. No viruses, autoimmune factors, or metabolic factors that could have caused hepatitis could be found. A lymphocyte transformation test was not performed. A liver biopsy was compatible with drug-related acute hepatitis. When gliclazide was withdrawn she improved. She took glibenclamide and recovered fully within 6 weeks. 

Thyroid hormones govern the body s metabolic rate. This means that the metabolism of nutrients and subsequent cellular utilization or storage rate is dependent upon blood circulatory thyroid hormone levels. Higher levels result in elevated over all metabolic rate providing that other metabolic factors are accommodated also. 

Guggulsterones Z and E seem to have the greatest effect upon stimulation of thyroid hormone, though other substrates of the herb commiphora mukul may effect different metabolic factors as well. Thus far, research suggests this is a result of guggulsterones Z E stimulation of TSH (Thyroid-Stimulating-Hormone) production. This results in an increase in Thyroid gland T-4 production and subsequent liver conversion to the more active T-3 hormone. 

Did you know that our body s make Des (1-3) IGF-1 naturally Most un-informed individuals claim other wise, but it is true. When an athlete trains lactic acid builds up in muscle tissue. As we know, there is always IGF-1 / GH present in the blood stream and tissues (including muscle) from prior work-outs and other metabolic factors. That lactic acid bum triggers IGF-l/GH secretion from both prior and present work-outs. Unfortunately, lactic acid destroys some of the IGF-1 present in muscles being trained. But wait, this is good too ... 

Physical (e.g., heat shock, ionizing radiation) and physiological (e.g., hypoxia) stresses, along with metabolic factors (e.g., glucose), induce specific gene expression by mechanisms involving DNA sequence specific transcription factors (Table 2.1). 

Rosmond R, Eriksson E, Bjorntorp P. Personality disorders in relation to anthropometric, endocrine and metabolic factors. J Endocrinol Invest 1999 22 279-288. 

To avoid confounds of metabolic factors and acute stress, allow food and water ad libitum prior to performing the sucrose consumption test. However, some strains may have altered water consumption (e.g., polydypsia), and the sucrose consumption test may not always be suitable for such strains. For example, this test may be unsuitable for diabetic (e.g, Hk2tmlLaak/Flk2+) Gr obese strains with altered water consumption. 

Because genetic effects in man cannot be reliably predicted from submammalian tests, smother alternative for quantitative risk estimation is to rely on data on the mouse. Despite reservations about the sensitivity of mouse tests and the statistical power of experiments with small numbers of animals, an in vivo mammalian system incorporates the more relevant biologic and metabolic factors necessary to make quantitative human risk estimates. 

A further consideration is which barbiturate to employ. We recommend the use of barbital because this substance, in contrast to many other barbiturates, undergoes no metabolism (Remmer 1972 Simon et al. 1992). For this reason, results obtained can be more readily interpreted in terms of a pharmacological interaction without confounding by pharmacokinetic or metabolic factors. 

Being one of the long-time standards in basic psychopharmacology, there are few major variants to the procedure apart from the kind of barbiturate employed. Several barbiturates undergo clear hepatic metabolism, for example pentobarbital and phenobarbital, thereby confounding interpretations because of pharmacokinetic and metabolic factors. Indeed, one modification of the method has been specifically employed to estimate enzyme induction in the liver as indicated by more rapid barbiturate metabolism. Animals given a pre-exposure to a test substance are then exposed to a standard dose of phenobarbital (80 mg/kg i.p.) 24 hours later and assessed for sleep duration. The presence or absence of a decrease in sleep duration is taken as an index of the hepatic enzyme induction produced by the test substance (Kushikata et al. 2003). 

In addition to factors Influencing luminal uptake of zinc, transfer across the basolateral membrane has been shown to be dependent on the concentration of albumin in the portal circulation (33). These investigations suggest that metabolic factors which affect the albumin concentration in the plasma may also affect the rate of portal zinc transfer. It should be noted that EDTA did not enhance zinc accumulation within the mucosal cells yet it Increased transfer to the vascular perfusate. These results suggest that basolateral membrane transport of zinc is enhanced by EDTA. We have proposed (35), as has Davies (38), that basolateral transport to the circulation is the rate limiting phase of zinc absorption. Since EDTA and zinc might be transported as a complex (42), the latter may transverse this barrier more easily and thus Increase zinc absorption. 

Conney, A. H., in "Metabolic Factors Controlling Drug Action, p. 250, B B. Brodie, E- G. Erdos, eds., Pergamon Press, London, 1962. 

Figure 2. Metabolic factors affecting the fate and persistence...

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